functions returning double or float inspection

functions returning double or float inspection

[Gene Smith]

I have been experimenting with function that return doubles in gcc such 
as c = pow(x,y). They work OK and I can inspect the float/double c 
return value (as a pop-up or as a watch) and it is ok. But if I inspect 
pow(x,y) itself (highlighting the function call with the mouse or 
evaluating in a watch window or print /f pow(x,y) in the console) I see 
usually an integer value with no decimal or an incorrect real value. Is 
this a bug or am I doing something wrong when letting insight/gdb 
calculate a float/double function value?

-gene

Re: functions returning double or float inspection

[Gene Smith]

Gene Smith wrote:
> I have been experimenting with function that return doubles in gcc such 
> as c = pow(x,y). They work OK and I can inspect the float/double c 
> return value (as a pop-up or as a watch) and it is ok. But if I inspect 
> pow(x,y) itself (highlighting the function call with the mouse or 
> evaluating in a watch window or print /f pow(x,y) in the console) I see 
> usually an integer value with no decimal or an incorrect real value. Is 
> this a bug or am I doing something wrong when letting insight/gdb 
> calculate a float/double function value?
> 
> -gene

Well, to quickly answer my own question see 
http://sourceware.org/gdb/wiki/FAQ .

<quote>
GDB reports a nonsensical return value from an inferior function call. 
What's going on?

     * GDB doesn't know the return type nor the type of the arguments 
for that function call, because there's no debug information available 
for it. Either provide debuginfo for the program or library which 
contains the function, or cast the function to a function pointer of the 
appropriate signature.

       For example, to call fabs, which takes a double and returns a 
double, use:

       (gdb) print ((double (*) (double)) fabs) ( -1.25 )
<end quote>

In my case
print ((double (*) (double,double) pow(x,y)
works for in the console. Pop-up and watch would require the libary 
built with debug info to see the correct values I think.